Means for protecting electric systems.



Witnesses:

E. E. F. CREIGHTON.

MEANS FOR PROTECTING ELECTRIC SYSTEMS.

APPLICATION FILED AUG. 15. I914.

1,273,744. Patented Jm '23,'191&

' Inventor- "EIrneY-E-FCrei h'ton, r

is-z qitbrng g. v

UNITED STATES. PATENT orrroa.

ELMER E. r. cnmon'ron, or SCHENECTADY, new YORK, Assmnon To GENERAL ELECTRIC COMPANY, A CORPORATION or NEW YORK.

MEANS FOR PROTECTING ELECTRIC SYSTEMS.

1,273,744. Original application filed m 13, 1912,

To all whom it may concern:

Be it known that I, ELMER E. F. CREIGH- TON, a citizen of the United States, residing at Schenectady, county of Schenectady,

State of New York, have invented Certain new and useful Improvements in Means for Protecting Electric Systems, of which the following is a specification; 1

The objectofmy invention isto give greater continuity of electrical service from transmission lines. The apparatus is particularly adapted to the conditions of multi- -ple feeders that exist on nearly all large transmission systems.

Mypresent application is a division of an application filed by me May 13, 1912,-Serial No. 696,930, means for protecting electric systems, and relates particularly to the means for indicating the faulty feeder which is used in connection therewith.

In order properly to understand the function of the protective apparatus, it is necessary to review the class of troubles that cause interruptions of service on electric systems, and the nature of the troubles. Trouble sometimes occurs by reasons of faults in cables which, though they may then exist in an embryonic state, are not developed by the necessarily brief high potential tests before installation, but develop only after -installation and more or less' 'use. Aside from the faults which may exist at such tests, the methods of installing often introduce weak spots in the joints between the sections of the lines. These weak spots develop gradually into accidental grounds. Another source of weakness comes from electrolytic action on the sheaths of cables which finally bares the insulation to the deterioratin action of the surrounding elements. T is production of these faults seems inevitable, although they can be minimized by careful work and selection of materials and 9 rigid inspection. My invention is adapted to. protect a system grounded by the development of any of such faults or grounds produced in any other way. There are certain effects produced when any fault develops into a grounded phase. The electrostatic capacity of the whole system is suddenly unbalanced, and there 'isa continual variation in these relations due to the areat the fault. The surges that are Specification of Letters Yatent.

cables are damaged. Finally, the arcing Patented July 23, 191s.

Serial No. 696,930. Divided and this application filed August 15, 1914. Serial No. 856,976.

thereby created course around the system, building up high resonant voltages in certain localities and damaging the insulation in general by the brush discharge resulting from the high frequencies. During this time of arcing ground, the station attendant is helpless. He knows that there is trouble but has no means of locating or suppressing it without disconnecting the: entire system, and thus interrupting service. uWith a continuance of such conditions, it almost invariably happens that apparatus and other ground forms into a short circuitand then a more or less widespread interruption is caused by the operation of overload. circuit breakers by the excessive currents which flow in the short circuit. Furthermore, great damage is liable to result. to other lines in the neighborhood of the faulty one. The apparatus which .is herein described is designed to perform the following useful functions: First,- to test the system to discover incipient faults in the insulation at a time of the day, night, or week most favorfeeders are available; second, within a small fraction of a second afterthe development,

of a fault, to locate on which. one of the several feeders the fault has'occurred and also to indicate the phase at fault; third, ;to suppress arcing grounds, and thus suppress I all the dangerous surges which are thefefby' produced; fourth, to give'an added prptec tion to the most important piece of a paratus on a system, namely, the generator, during the brief interval that is necessary for the arcing ground suppressor to operate.

Up to the present, in the methods described for'localizing faulty feeders ,.no, aocount has been taken of the fact that the grounding currents on a system are; seldom constant. Therefore, apparatus which. is designed to operate o1' n0t.operate according to the value of the grounding current be comes unreliable in actual practioe Some devices,'if made sensitive, will produce false operations when the accidental currents-to ground are heavy. If such devices are made ter what the conditions of arcing ground invention attached thereto.

are, the relative increase of current in one feeder has a proportional increase in all the other feeders. However, if the forces engendered are caused to operate-on a common element, the common element will move in- "the direction of the strongest force.

In the accompanying drawing, which forms a part of this specification, there is illustrated diagrammatically a system of distribution involving my invention. Figure 1 illustrates diagrammatically a system of dis tribution including a generator, bus bars and three feeders with apparatus involving my Fig. 2 illustra-tesv diagrammatically parts of a localizer adapted for use with four feeders.

Before proceeding to. describe the othe parts of this system of protection, I shall describemore in detail the relations of the circuits to the localizer as they are shown in Fig. 1. In this description I shall designate the feeders as A, B and C, and shall follow this nomenclature through with corresponding numbers. The particular system illustrated is a threephase system and the phases I shall designate, as m, 'g and 2. A is a three-phase transformer or a group of three' single-phase current transformers, such as those used for instruments, the windings of which are so related and connected that no current is produced in the leads to the electrpmagnets, later described, tinder normal balanced operating conditions. B is a corresponding group of current transformers-on cable B, and C for cable 0..

These transformers may be the standard instrument transformers also supplying the in- 'struments, by which means it is possible to avoid the expense of special transformers. As far as the protective features are concerned, each group of transformers may be replaced by any transformer or group of transformers producing the desired results on the attached solenoids or electromagnets. By so connecting the current transformers I obtain a resultant current fromv each feeder which is .independent -of load current no.

matter how unbalanced such load current may be. As long as the current comingout one phase returns over one or bothof the other phases there ill be no resultant current. produced. One side of each of the secondary'circuits may be grounded in ordertogive safety against shock. Each of the transformer circuits is connected to an electromagnet or solenoid in the manner indicated; these electromagnets are shown at A B and C Since under normal conditions of operation the algebraic sum of the three currents in the three transformers on any feeder isequal to zero, no current under such conditions will pass through the electromagnets A B and C When, however, a ground takes place in the s St8ll'1, the electrostatic currents in the trans ormers of these three phases become unbalanced and there is a resultant current in the electromagnet's A B and C ,-the grounded feeder giving the greatest current. This will be explained in detail later. The three electromagnets A B and C have their axes spaced 120 apart and point to a common center. At this common center an armature 4 is placed. This armature is mounted on a freely moving pendulum pivoted at the upper end at 5. Under this condition of design, no matter what the absolute values of the currents are in the electromagnets A", B and C the electromagnet giving the-strongest pull will draw the armature in its direction. The apparatus, being arranged in, this manner; is so independent of absolute values that it may be made as sensitive as desirable and is independent of the erratic changes in grounding current. These are the important features referred to above and are not applicable to a ground localizer alone but to localizers of various conditions.

It will, of course, be understood that it is essential'that the solenoids produce equal stresses on the armature on the occurrence of a faulton the system elsewhere than on rious ways as by using difi'erent numbers of turns on the solenoids, differently positioning the solenoids relatively to the ar'- m'ature, using different numbers of turns on the transformer, etc. I prefer to construct the coils A B and C with the numbers of turns therein inversely proportioned to the electrostatic capacity of the-feeders to which they are respectively attached.

Prior to the occurrence of a ground, the 7 electrostatic currents flowing on each feeder through its group of transformers balance and hence the transformerstend to send no I current through the attached electromagnct.

On the occurrence of a ground on one phase, however, that-phase throughout the entire system assumes earth potential and there is no longer an equal'eXchange-of charging current between the phases. In other words, the currents in the three phases on each feeder will be unbalanced, causing a difference of potential at the terminals of the transformers: In the feeder that is ground- .ed, there is more unbalanced current than conditions existing at n"; any other.

magnets A, B and C, an 'dicators A, B and 0.

=inj any of the other feeders connected. to

thebus bars. It should be noted that the the transformer of the grounded feeder to these 1th. This in itself produces a differ- .l ntiationbetween the cables, 2'. 'e., a greater unbalanclng in the grounded feeder than i It is understood that the phenomena on grounding is not simple, but this short-explanation of what I now believetakes place is sufiicient for the purposes of ,thissPecification. Although the actual cult to explain, there is-no question about the result; all the groups of transformers {train the unbalanced condition, and the unba anc'ed, with the result: of a selection in the movement of the armature 4. The free moving pendulum is extended beyond the armature 4 so that in its movement toward n electromagn'et it will engage with alocal some sort of signal which feeder is grounded. The three local circuit contacts are'numbel ed; corresponding1 to the electrothe signal in- The circuits for these, indicators are completed through a batte or other source of electrical energy 7, anythe suspension point 5. The signal and C may be soar-ranged devices A B U hat when the signal is once made, it remni nseven after the contact at any one of ';thgcontacts A, B or C is broken.

A simple' device for this purpose is a drop indicator, although any other suitable indicator "finay be used. The devices-A, Band C 1 any may, however, be'relays in local circuits for operating more distant signals, switches or devices. Surges of short duratagxf'njay occur on the system from vari0us-G81ises'and the localizer should be so adjusted that while it will respond to a true grourul though an arcing one, it will not respondjtothese surges of short duration. In

other words, a time element should be pro- This time element- Vided in 'the localizer. maybe brought in by a proper adjustment of the length of the pendulum and by the 4 .With reference to the armature 4. It will stood that the adjustments should be such ill? that .while the localizer will not respond sufliciently-to close the contactsA, B and (J on the occurrence of transitory. surges of short duration, such as course around the system at various times, due to switching,

these contacts on the occurrence of a fault before the arcing ground suppressor can ground the system.

any instant are difiion the grou'nded cable is the mostwhich forms be underoperate and close I have now described how my novel localizer or-selective device operates on a system of distribution comprising three feeders. This type of localizer is especially applicable to systems of distribution comprising radial feeders, that-is feeders that tirely if the forces are equal, and assuming the feeder connected to either electromagnet 9 or 11 is grounded, there will be a resultant force in the direction of the electromagnet corresponding to the grounded feeder. There are four contacts 12,- 13, 14 and 15, corresponding to the electromagnets, and having the same physical relation thereto as already described with reference to Fig. 1. It will be understood from this how my system of balancing out currents may apply to .more than four feeders. The function then of the localizer is to instantly show which feeder is at fault.

.We now come to the suppressor of the arcing ground which is first formed on the development of a fault. An arcing ground produces surging on the 1t is necessary to eradicate the are as soon as possible. Any device which eradicates the arc,by dead grounding, or otherwise, is broadly suitable, but I prefer to use the de vice showndiagrammatically in Fig. 1, the subjectmatter of my prior applications, Serial No. 492,846 and No. 597,405. The particular device illustrated has already been described in detail in my system and hence application, Serial No. 597,405, and I will,

application SeruNo. 492,846 or electrostatically operaterl but, for purposes of illustration, that shown in Fig. 1 is operated electrostatically. There are threefixed electrostatic plates an, y fand 2 These plates exerta force onmo vable plates or", 1 and z". The three movable plates are attached to a common center, 18, which is a part of a pendulum. supported Fat against one of the three contacts 20, 21 or 22 to indicate the phase of the system grounded. Closing this contact also operates one of three phase switches all of which are inclosed with their accompanying mechanism at 23. Closing the proper switch makes a dead ground between the grounded phase and earth, and thus extinguishes the accidental are which has occurred on that phase at some unknown point on the system and prevents destructive surging. Since this suppressor is on the bus bars, it relieves the armature 4 of the localizer but the signal or other mechanism on the corresponding feeder having already responded gives an indication of the faulty feeder.

I have now described the method of localizing the fault and the method of suppressing it, and I will next dcscribdthe combination of apparatus for giving protection against the surges which occur during the brief time required for the operation of the suppressor. This apparatus includes an electrolytic cell or cells 26 connected between the neutral 24 of the generator and the ground The cell may be an aluminum one similar to those used as lightning arresters but no series gap is required. It is well known in the art that grounding the neutral of a system gives a great relief to the static strains in the system. If, however, this neutral is grounded through no resistance, then every ground on the line results in a short circuit, and an interruption of service. This is intrinsically an objectionable condition. If the neutral is grounded through a high resistance, then the protective value is very greatly lost by the obstruction of the oscillating currents in the resistance. Thisapplication of the electrolytic cell to the neutral gives all the advantages of the grounded system in absorbing abnormal potentials, and at the same time has none of the disadvantages of short C11- cuits thatoccur with the neutral grounded through no resistance. Since it is the natural characteristic of the aluminum film to become dissolved in its electrolyte, itis nec- 'essary to supply a charging device as shown by the-switch 27 for renewing the film from time to time. I have now added to the systemof protection a device for absorbing the surges duringthe brief intervals of time that these surges take place.

I now turn to the device, for the development of the incipient fault, which device may cooperate with the other devices to develop a'fault at a time when no great embarrassment will be caused and when it may be readily .corrected. This device consists of some sort of a (.lirect'current source 28, as a generator or a rectifier, which produces a DC potential which is superimon the AC potential waves on the sysposed This source 28 s connected between tem.

- w-hen there is ground and some neutral point of the. system by means of the switch 30. This neutral of the system may be an artificial one 29 produced by a combination of three reactances 31, 32 and 33 connected to the respectivephases m, y and 2, or may be the neutral of the generator. The idea of measuring resistance by this means, I am aware,

is well known in the art, but the'use of such a direct current generator to aid in produc ing the proper potential to strain the in sulation for test is, I believe, novel. .The impression of this direct current on the system requires very little energy and combines with the alternating currents from'80 the generator to produce the high poten,- tials required. It is a well known fact that any piece of insulation can stand a greater direct current potential than it can alternatingpotential. Therefore, the testing of such a system when it is dead, by direct current, is not an adequate test, but the imposition of the direct current potential on the system when operating under alternating currents has the advantages of an alternating current test. Such tests may be made by alternating currents but such testing ,requires not only a very large kilovolt-ampere capacityin the testing devicebut-also engenders possiblecombinations with the alternating current of the system to give variable voltages, and combinations with the electrostatic capacities to give resonance, both of which are objectionable. The system I propose takes advantage of the alternating'current furnished by the generator to give the effects on the insulation of alternating currents and at the sani'e time requires very little energy from the superimposed direct current potential from the generator 28. This developer of faults then completes the system for the preservation of continuity of electric service.

The attachn'ient of the protective features to the system provides constant protection for faults which may develop at any time; the combination therewith of the testing means I regard as a desirable feature, since by this means, as has been before intimated, the system may be tested out at some time but little demand being made upon it, and any faults .which are near the point of development, developed at that time. .The development of a fault under test .causes the operation of the protecting devices, and thus protects the system against the injury which it might sustain the same as though the fault developed naturally. If necessary, the faulty feeder may be cut out and other provision made for supplying the portion of the -load normally supplied. by that feeder, before the demand can become great. The fault may even be located and the feeder repaired before its service is again required. I

IOI

Y normal conditions on the feeders, means to be actuated on the occurrence of such ab normal conditions, a local circuit for each of said means, and an armature controlled by said solenoids for, closing the proper circuit, the solenoids and armature being so constructed and related that similar abnormalities in the feeders producestresses by the solenoids on the armature inversely proportional to the electrostatic capacities of the feeders. I a

2. The combination with a system of distribution including three-or more feeders, of means to be actuated on the occurrence of abnormal conditions on any of said feeders, an armature for controlling the actuation of said means, and means connected to each of said feeders and energized thereby, said armature belng under the oint control of those last mentioned means attached to a sound and a faulty feeder; said means being so constructed and related as to produce equal stresses on the armature on the occurrence of abnormalities in the feeders due to a fault elsewhere than thereon.

3, The combination with a system of distribution including three or more feeders, of means to be actuated on the occurrence of abnormal conditions on any of said feeders, mechanism for actuating said means, and means connected to each of said feeders and energized thereby, said actuating mechanism being under the joint control of the last mentioned means, said last mentioned means being so constructed and related to the. actuating mechanism as to balance each other and produce no movement thereof on the production of equal stresses by said means, and to produce equal stresses on the occurrence of a fault elsewhere than on the feeders to which they are attached.

4. The combination with a system of distribution including three or more feeders, of indicating means to be actuated on the occurrence of abnormal conditions on any of said feeders, mechanism for actuating said means, and means connected to each of said feeders and energized thereby, said. actuating mechanism being under the joint control of the last mentioned means, said last mentioned means being so constructed and 'related to the actuating mechanism as to balance each other and produce no movement thereof on the production of equal stresses thereon by said means, and to produce equal stresses on said mechanism on .the occurrence of a fault elsewhere'than on the feeders to which they are attached. v 5. The combination with a. system of distribution including three or more feeders,- of means to be actuated on the occurrence of abnormal conditions" on any of said feeders, Y

mechanism for actuating said means, and means connected to each of said feeders and energized thereb said actuating mechanism being under t e joint control of the last mentioned means, said last mentioned means being so constructedand related to the actuating mechanism that those attached to healthy feeders balance each other and allow movement, of the mechanism responsive to the action of the-means attached to the faulty feeder. I y

6. The combination with a system of distribution including three or more feeders, of.

means to be actuated on the occurrence of 4 abnormal conditions on any of said feeders, mechanism in common for actuating said means, and means connected to each ofsaid feeders and energized thereby, said actuating mechanism being under the joint con trol of the last mentioned means, said last mentioned means being so constructedand related to the actuating mechanism that those producing equal stresses thereon balance each otherand allow movement of the mechanism responsive to the action of the means produclug thereon a different stress. 7 The combination-with a system of dis-- tribution including three or more feeders, of

transformers operatively related thereto, a

solenoid for each feeder connected to the transformers, the transformer windings being so connected and related as to deliver no current to the solenoids under normal operating-conditions of the feeders and an armature, the solenoids being spaced at equal angular distances from each other about said armature.

8. The combination with a system of dis tribution including three or more feeders, of transformers operatively related thereto,

a solenoid for each feeder connected to the transformers, the transformer windings being soconnected and related as to deliver no current to the solenoids under the nor.-

,mally-balanccd condition of the feeders, and

an armature, the solenoids being spaced. atequal angular distances from each other about said armature. l

9. The combination wit alsystem of distribution including a plurality of feeders, of transformers o eratlvely related thereto, a solenoid for each feeder connected to the. transformers, the transformer windings being so connected and related as to deliver no current to the solenoids under the normally balanced condition of feeders, and an armature, the solenoids being spaced at equal angular distances from each other. thereabout, and being so constructed and re- 7 lated to the armature as to produce thereon on the occurrence of equal currents in the solenoids, stresses 'WlllOll bear a relation to tion having threevor more feeders, compriseachother inversely proportional to the electrostatic capacity of their respective feeders.

10. The combination with a system of distribution including a plurality of feeders, of transformers attached thereto, a solenoid for each feeder connected to the transformers, the transformer windings being so connected and related as to deliver no current to the solenoids under the normally balanced condition of the feeders,.and an armature, the solenoids being spaced at equal angular distances from each other thereabout, the number of turns on the solenoids being inversely proportional to the electrostatic capacity of their respective feeders.

11. The combination with a system of distribution including three or more feeders, of an indicatorfor each feeder, a differentially operated member controlling the operation of said indicators, and electrorespon' sivemcans for each feeder operative in response to the unbalanced current flowing when any one of said feeders is grounded for selectively actuating said member to cause the operation of that indicator corresponding to the feeder having the greatest unbalanced current.

12. The combination with a system of distribution including three or more feeders,

of means selectively actuated on the occur-- rence of a fault, and separate means for each feeder energized in response to charging current flowing'when one of said feeders is grounded said separate means all acting on the-first mentioned means.

13. The combination with a system of distribution comprising three or more feeders,

of a localizer of a fault comprising differential means responsive to the unbalanced eiectrostatic charging current of said feeder due to the occurrence of the fault for selectively indicating the faulty feeder.

1a. A. device for selectively indicating a grounded feeder on a system of distribuing means actuated in response to the resultant current of each feeder,.an indicator operated in response to each of said means, and means difl erentially'operated' by said first mentioned means corresponding to the feeder grounded. i

15. A localizer of a ground on. a system of distribution having three or more feeders, comprising an electroresponsive' device energized in response to the result-antennrent n each feeder, an indicator corresponding to each feeder, and a common member differentially movable in response to said electroresponsive devices to operate that indicator corresponding to the feeder l aving the greatest resultant current.

16. A localizer of a ground on a system of distribution having a plurality of feeders comprising a device for each feederoperated in response to the resultant current in its respective feeder, means differentially congreatest unbalanced current, and indicators operative in response to the. movement of said'member to maintain an indication of the position of said member after said member has returned to its initial position.

Inwitness whereof, I have hereunto set my hand this 14th day of August, 1914.

ELMER E. F. GREIGHTON.-

. W'itnesses:

BENJAMIN B. HULL, HELEN Onronn. 

